Die Therapie des häufigsten primären Hirntumors bei Erwachsenen, des Glioblastoms, gestaltet sich aufgrund der relativen Resistenz gegen Bestrahlung und Zytostatika schwierig und resultiert in einer äußerst schlechten Prognose. Ziel dieser Arbeit war die Identifikation von zellulären Faktoren, die bei einer Behandlung mit dem neuartigen onkolytischen Virus Ad5-Delo3RGD (ΔE1A-13S, ΔE19K, ΔE3, zusätzliches RGD-Motiv) eine Bedeutung hinsichtlich des Ansprechens auf die Therapie haben. Dazu erfolgte nach der Transduktion von Gliomzellen mit adenoviralen Vektoren, mit unterschiedlichem E1A-Status, eine Analyse der Modulation der globalen Genexpression. Die E1A-Deletante, Ad5-Ad312, war replikationsinkompetent in Gliomzellen und hatte infolgedessen nur einen marginalen Einfluss auf Genebene und keine biologischen Effekte auf Proteinebene. Das Wildtypvirus (Ad5-wt) mit intakter und das onkolytische Virus (Ad5-Delo3RGD) mit mutierter E1A-Region induzierten eine starke Modifikation der zellulären Genexpression in Gliomzellen. Die Transduktion der Gliomzellen mit Wildtypvirus bzw. onkolytischen Virus resultierte in einer bis zu 60 %-igen Hemmung der Sekretion des Angiogenesefaktors VEGF. Fernerhin konnte in Glioblastomzellen gezeigt werden, dass Ad5-wt und Ad5-Delo3RGD eine 50 bis 60 %-ige Inhibition der Sekretion von TGF-β2, sowie eine bis zu 65 %-ige Hemmung der Transkriptionsaktivität des TGF-β-Signalwegs induzierten. Damit reprimieren besagte Viren zelluläre Faktoren, deren Expression im Gliom mit einer schlechten Prognose korreliert ist. Aufgrund dieser Daten konnte für maligne Gliome ein Modell von Ad5-Delo3RGD-Therapie relevanten zellulären Faktoren entwickelt werden, welches den Zusammenhang zwischen TGF-β2, VEGF bzw. MIR-181 und der Virotherapie verdeutlicht. Mit Hilfe dieses Modells steigt das Verständnis um die antineoplastische Aktivität des onkolytischen Virus, und ermöglicht damit eine Verbesserung der Ad5-Delo3RGD-basierten Therapie. / Glioblastoma is the most common type of brain tumor among adults. The therapy is very difficult, due to its relative resistance to radiation and zytostatica, and often results in fatal prognosis. The main objective of this thesis was the identification of cellular factors associated with therapy response to adenoviral treatment using the newly developed oncolytic virus Ad5-Delo3RGD. Therefore, after viral transduction of glioma cells with adenoviral vectors, using E1A-wildtype and -mutant viruses, an analysis of the modulation of mRNA expression profiles was conducted. The E1A deletion mutant Ad5-Ad312 was replication-deficient in glioma cells and therefore had only marginal influence of host gene transcription level and no biological effect on protein level. Both, wildtype adenovirus type 5 (Ad5-wt), with intact E1A, and oncolytic virus (Ad5-Delo3RGD), with mutated E1A, induced strong modifications of gene expression profiles in glioma cells. The transduction of glioma cells with wildtype or oncolytic virus resulted in a 60 % reduced secretion of the angionesis factor Vascular Endothelial Growth Factor (VEGF). In addition it was shown that Ad5-wt and Ad5-Delo3RGD induced a reduced secretion of TGF-ß2 by 50 to 60 % and a repression of the SMAD2/SMAD3/SMAD4-specific transcription activity up to 65 %. Thus the viruses inhibit cellular factors, which expression is corelated to a weak prognosis. Based on this data a new model for malign glioma was developed, which illustrates the relationship between virotherapy and the cellular factors TGF-β2, VEGF and MIR-181, which are associated with treatment response to Ad5-Delo3RGD-based therapy. The model helps to understand the basic antineoplastic activity of the oncolytic virus and therefore should help to improve Ad5-Delo3RGD-based therapy.

<p>As a means of further localising the interaction, truncated fragments derived from the C-terminal region of YB-1, were tested for their interaction with the RING finger domain of RBBP6 using three different assays: a directed yeast 2-hybrid assay, co-immunoprecipitation and NMR chemical shift perturbation analysis. Our results suggest that the entire 62 amino acid region at the C-terminal domain of YB-1 may be involved in the interaction with RBBP6. Using chemical shift perturbation analysis, this study provides an indication of where YB-1 binds to the RING finger. This represents the first step towards the design of therapeutics aimed at modulating the interaction between RBBP6 and YB-1 as a means of targeting the oncogenic effects of YB-1. In order to identify E2 enzymes involved in the ubiquitination of YB-1, we examined the efficiencies of selected E2s in an in vitro ubiquitination assay. UbcH5c and UbcH7 were both found to catalyse the ubiquitination of YB-1 in conjuction with RBBP6, whereas Ubc13 was not. Finally, we show using NMR that two single-point mutations of the RING finger-like domain are sufficient to abolish homodimerisation of the domain. These will be used in future studies to investigate the requirement for homodimerisation on the ubiquitination activity of RBBP6.</p>

<p>As a means of further localising the interaction, truncated fragments derived from the C-terminal region of YB-1, were tested for their interaction with the RING finger domain of RBBP6 using three different assays: a directed yeast 2-hybrid assay, co-immunoprecipitation and NMR chemical shift perturbation analysis. Our results suggest that the entire 62 amino acid region at the C-terminal domain of YB-1 may be involved in the interaction with RBBP6. Using chemical shift perturbation analysis, this study provides an indication of where YB-1 binds to the RING finger. This represents the first step towards the design of therapeutics aimed at modulating the interaction between RBBP6 and YB-1 as a means of targeting the oncogenic effects of YB-1. In order to identify E2 enzymes involved in the ubiquitination of YB-1, we examined the efficiencies of selected E2s in an in vitro ubiquitination assay. UbcH5c and UbcH7 were both found to catalyse the ubiquitination of YB-1 in conjuction with RBBP6, whereas Ubc13 was not. Finally, we show using NMR that two single-point mutations of the RING finger-like domain are sufficient to abolish homodimerisation of the domain. These will be used in future studies to investigate the requirement for homodimerisation on the ubiquitination activity of RBBP6.</p>

Philosophiae Doctor - PhD / Retinoblastoma Binding Protein 6 (RBBP6) is a 250 kDa multi-domain protein that has been implicated in diverse cellular processes including apoptosis, mRNA processing and cell cycle regulation. Many of these functions are likely to be related to its interaction with tumour suppressor proteins p53 and the Retinoblastoma protein (pRb), and the oncogenic Y-Box Binding Protein-1 (YB-1). RBBP6 inhibits the binding of p53 to DNA and enhances the HDM2-mediated ubiquitination and proteasomal degradation of p53. Disruption of RBBP6 leads to an embryonic lethal phenotype in mice as a result of widespread p53-mediated apoptosis. RBBP6 promotes ubiquitination and degradation of YB-1, leading to its proteasomal degradation in vivo.The first part of this thesis describes in vitro investigations of the interaction betweenbacterially-expressed human p53 and fragments of human RBBP6 previously identified as interacting with p53, in an attempt to further localise the region of interaction on both proteins. GST-pull down assays and immunoprecipitation assays confirmed the interaction, and localised it to the core DNA binding domain of p53 and a region corresponding to residues 1422-1668 of RBBP6. However in Nuclear Magnetic Resonance (NMR) chemical shift perturbation assays no evidence was found for the interaction. NMR showed the relevant region of RBBP6 to be unfolded,and no evidence was found for interaction-induced folding. The R273H mutant of the p53 core domain did not abolish the interaction, in contrast to reports that the corresponding murine mutation (R270C) did abolish the interaction.The second part of this thesis describes in vitro investigations of the ubiquitination of YB-1 by RBBP6. A fragment corresponding to the first 335 residues of RBBP6,denoted R3, was expressed in bacteria and found to be soluble. Contrary to expectation, in a fully in vitro assay R3 was not able to ubiquitinate YB-1. However,following addition of human cell lysate, YB-1 was degraded in an R3-dependent and proteasome-dependent manner, indicating that R3 is required for ubiquitination and proteasomal degradation of YB-1. However R3 is not sufficient, with one or more factors being supplied by the cell lysate. In view of the pro-tumourigenic effects of YB-1 in many human cancers, these results lay the foundation for an understanding of the regulatory effect of RBBP6 on YB-1 and its potential role in anti-tumour therapy.

Magister Scientiae - MSc / As a means of further localising the interaction, truncated fragments derived from the C-terminal region of YB-1, were tested for their interaction with the RING finger domain of RBBP6 using three different assays: a directed yeast 2-hybrid assay, co-immunoprecipitation and NMR chemical shift perturbation analysis. Our results suggest that the entire 62 amino acid region at the C-terminal domain of YB-1 may be involved in the interaction with RBBP6. Using chemical shift perturbation analysis, this study provides an indication of where YB-1 binds to the RING finger. This represents the first step towards the design of therapeutics aimed at modulating the interaction between RBBP6 and YB-1 as a means of targeting the oncogenic effects of YB-1. In order to identify E2 enzymes involved in the ubiquitination of YB-1, we examined the efficiencies of selected E2s in an in vitro ubiquitination assay. UbcH5c and UbcH7 were both found to catalyse the ubiquitination of YB-1 in conjuction with RBBP6, whereas Ubc13 was not. Finally, we show using NMR that two single-point mutations of the RING finger-like domain are sufficient to abolish homodimerisation of the domain. These will be used in future studies to investigate the requirement for homodimerisation on the ubiquitination activity of RBBP6. / South Africa

YB-1 (Y-Box-binding Protein 1) est une protéine multifonctionnelle qui affecte plusieurs processus biologiques incluant la transcription, la traduction, la réparation de l’ADN et le développement embryonnaire. YB-1 appartient à une large famille de protéines liant l’ADN / l’ARN avec un motif très conservé à travers l’évolution appelé CSD (Cold Shock Domain). YB-1 est une protéine surexprimée dans plusieurs tumeurs et affecte les différentes voies de développement des cancers. Une surexpression de la protéine YB-1 rend les cellules des cancers du sein, ovariens et colorectaux résistants aux composés à base de platine. La protéine YB-1 présente beaucoup d’intérêts thérapeutiques pour lutter contre les cancers. Bien que plusieurs approches visant à cibler la protéine YB-1 aient été développées pour prévenir et traiter des patients, un effort substantiel reste nécessaire puisque la fonction multiple de la protéine YB-1 doit être prise en considération. Les buts de ce projet sont d’identifier les partenaires de la protéine YB-1 impliqués au niveau de la chimiorésistance dans différents types de cancers aux composés à base de platine et de développer de nouvelles approches thérapeutiques potentielles. Pendant cette étude, nous avons identifié les protéines NONO et RALY comme nouveaux partenaires de la protéine YB-1 dans les cellules des cancers colorectaux. Nous avons démontré que les protéines NONO et RALY sont impliquées au niveau de la chimiorésistance des cellules des cancers colorectaux aux composés à base de platine. Cette étude a aussi permis d’identifier RPS4X comme nouveau partenaire de la protéine YB-1 impliqué au niveau de la chimiorésistance des cellules du cancer du sein et ovarien au cisplatine. La protéine RPS4X est un nouveau biomarqueur prédictif et pronostic pour les patientes atteintes du cancer de l’ovaire et traitées au cisplatine. Le biomarqueur RPS4X représente ainsi, une nouvelle cible thérapeutique potentielle pour contrecarrer la chimiorésistance des cancers aux composés à base de platine incluant les tumeurs avec une surexpression de la protéine YB-1. Le niveau d’expression de la protéine RPS4X pourrait être utilisé en première ligne pour la sélection des thérapies pour des patientes atteintes des cancers ovariens et du sein. / YB-1 (Y-Box-binding Protein 1) is a multifunctional protein involved in several cellular processes including transcription, translation and DNA repair. YB-1 is important for late-stage embryonic development and belongs to the family of DNA/RNA-binding proteins with an evolutionarily ancient conserved Cold Shock Domain (CSD). YB-1 is overexpressed in many malignant tissues and plays an important role in the development of cancer. Many studies reported that high expression of YB-1 protein is associated with a worse prognosis in cancer patients. Moreover, an overexpression of YB-1 protein in breast, colorectal and ovarian cancer cell lines induced chemoresistance to platinum agents. YB-1 protein is a good therapeutic target to counteract platinum resistance in cancer. Different strategies for novel therapeutic approaches targeting YB-1 protein were used to prevent and treat people with cancer. The use of YB-1 as a therapeutic targets is still a big challenge in research and its multifunctional properties should be taken into consideration when developing a new therapy against YB-1. The goals of this project are to identify YB-1-interacting proteins required for platinum agents resistance in cancer cell lines and to develop a potential therapeutic target to treat cancers. During this study, NONO and RALY proteins were identified as new partners of YB-1 protein in colorectal cancer cell lines. We proved that NONO and RALY are significant potential target to counteract oxaliplatin resistance in colorectal cancers including tumors overexpressing the YB-1 protein. In addition, we found RPS4X protein as new a partner of YB-1 involved in cisplatin resistance in beast and ovarian cancers. These results suggest that the RPS4X protein is a significant potential target to counteract cisplatin resistance in breast and ovarian cancers. Also, we have established that RPS4X is a new promising prognostic marker for patients with high-grade serous ovarian cancer. More importantly, RPS4X is shown to be predictive of cisplatin response. RPS4X could thus be useful when selecting the first line therapies for patients with breast and ovarian cancer.

Einer der Gründe für das Scheitern derzeitiger Behandlungsmethoden beim Brustkrebs ist die Resistenz gegenüber der angewandten Chemotherapie. Eine große Rolle bei der Entstehung der Multiplen Medikamentenresistenz spielt das MDR1-Gen und sein Genprodukt, das P-Glykoprotein. Das Y-Box-Protein YB-1 reguliert die Expression des MDR1-Gens; eine Überexpression und nukleäre Lokalisation von YB-1 geht im Brustkrebs mit einer gesteigerten P-Glykoprotein Expression einher. In dieser Arbeit wurden Gewebeproben von 83 Brustkrebspatientinnen auf eine YB-1 Überexpression im Tumor und im peritumoralen Epithel untersucht. YB-1 wurde mittels der immunhistochemischen APAAP-Methode an Formalin-fixierten, in Paraffin eingebetteten Brustkrebsgewebeproben nachgewiesen. Die klinische Relevanz der YB-1 Expression wurde untersucht, indem sie mit dem klinischen Verlauf in einem mittleren Beobachtungszeitraum von 61 Monaten und etablierten biologischen Tumorfaktoren wie Lymphknotenstatus, histologisches Grading, Tumorgröße, Hormonrezeptorstatus, uPA und PAI-1 verglichen wurde. In der Kohorte der Patientinnen mit einer postoperativen adjuvanten Chemotherapie zeigte sich eine 5-Jahres-Rezidivrate von 68 % bei einer hohen YB-1 Expression im Tumor und eine Rückfallrate von 39 % bei einer niedrigen YB-1 Expression. Unter Beachtung auch der YB-1 Expression im peritumoralen Epithel konnte ein noch größerer Unterschied hinsichtlich der 5-Jahres-Rezidivrate festgestellt werden. Diese betrug bei Patientinnen mit einer hohen YB-1 Expression 66 %, während bei Patientinnen mit einer niedrigen YB-1 Expression im Nachbeobachtungszeitraum kein Rezidiv festgestellt wurde. Bei der Gegenüberstellung der 5-Jahres-Rezidivraten in der Kohorte der Patientinnen ohne Zytostatikatherapie zeigte sich eine Rückfallrate von 30 % bei einer hohen YB-1 Expression und eine Rückfallrate von 0 % bei einer niedrigen YB-1 Expression. Eine hohe YB-1 Expression war demnach in beiden Kohorten mit einer schlechteren klinischen Prognose assoziiert. Das Ergebnis in der Gruppe der Patientinnen ohne postoperative Chemotherapie zeigt, dass YB-1 mit der Tumoraggressivität beim Brustkrebs korreliert. Eine Korrelation zwischen der YB-1 Expression und den etablierten prognostischen Faktoren Lymphknotenstatus, Tumorgröße und histologisches Grading konnte nicht festgestellt werden. Es wurde jedoch eine signifikante negative Korrelation zwischen der YB-1 Expression und dem Hormonrezeptorstatus und eine positive Korrelation zwischen YB-1 und den Faktoren uPA und PAI-1 gefunden. In dieser Arbeit wurde gezeigt, dass YB-1 eine klinische Relevanz besitzt mit Hinblick sowohl auf eine prognostische als auch eine prädiktive Bedeutung bei der Identifikation von Hoch-Risiko-Patientinnen im Brustkrebs in Ab- und Anwesenheit einer postoperativen Chemotherapie. / Intrinsic or acquired resistance to chemotherapy is one of the reasons for failure of current treatment regimens in breast cancer patients. P-glycoprotein and its gene mdr1 plays a major role in the development of a multi-drug resistant tumor phenotype. The Y-box protein YB-1 regulates the expression of mdr1. In human breast cancer, overexpression and nuclear localization is associated with upregulation of P-glycoprotein. In this study, tissues of 83 breast cancer patients have been analyzed with regard to YB-1 overexpression in tumor tissue and in surrounding benign breast epithelial cells. YB-1 has been detached by the immunohistochemical APAAP-method using formalin-fixed, paraffin-embedded breast cancer tissues. Clinical relevance of YB-1 expression was analyzed by comparing it with clinical outcome after a median follow-up of 61 months and with tumor biological factors lymph-node status, tumor size, histological grading, hormone-receptor status and the factors uPA and PAI-1. In patients who received postoperative chemotherapy, the 5-year-relapse rate was 68% in patients with high YB-1 expression in tumor cells and 39% in patients with low expression. With regard to YB-1 expression in surrounding benign breast epithelial cells, the 5-year-relapse rate was 66% in patients with high YB-1 expression whereas in patients with low expression no relapse has been observed so far. YB-1 thus indicates clinical drug resistance in breast cancer. In patients who received no chemotherapy, the 5-year-relapse rate was 30% in patients with high YB-1 expression whereas in patients with low YB-1 expression no relapse occurred. YB-1 thus correlates with breast cancer aggressiveness. In both groups high YB-1 expression was associated with poor clinical outcome. A correlation between YB-1 and tumor biological factors lymph-node status, tumor size and histological grading has not been found. But a significant negative correlation has been observed between YB-1 and hormone-receptor status and a positive correlation between YB-1 and uPA and PAI-1. This dissertation could show the clinical relevance of YB-1 with regard to a prognostic and predictive significance by identifying a high-risk group of breast cancer patients both in presence and absence of postoperative chemotherapy.

No description available.

Despite recent advances in antiretroviral therapy, nearly 37 million people continue to live with human immunodeficiency virus (HIV). Basic and applied research on the assembly of HIV could be enhanced by using a genetically tractable organism, such as yeast, rather than mammalian cells. While previous studies showed that expression of the HIV Gag polyprotein in Saccharomyces cerevisiae spheroplasts resulted in the production of virus-like particles (VLPs), many questions regarding the utility of yeast in HIV assembly remain uninvestigated. Here, we report use of S. cerevisiae for both the production of VLPs with selectively packaged RNA and to evaluate the human Y-box-binding protein 1 (YB-1) in selective RNA packaging into VLPs. Our data reveal: (1) When co-expressed alongside HIV-1 Gag, an RNA mammalian expression cassette is selectively encapsidated and released in VLPs produced from spheroplasts; (2) Inclusion of the 5’UTR-5’Gag RNA upstream of the mammalian expression cassette greatly increased the selectivity to which non-viral RNA was packaged into VLPs; and (3) heterologous expression of the human YB-1 protein in S. cerevisiae did not facilitate the selective packaging of viral RNA into VLPs, likely due to inability to bind upstream elements in the HIV-1 viral RNA. Overall, this research provides a key first step in the use of yeast for the production of viral vectors used in gene therapy, and lays a foundation for further experiments investigating the role of YB-1 and other host proteins in selective RNA packaging.

No description available.